1. Field of the Invention
The present invention relates to a digital recording and reproducing apparatus (digital VTR) for recording and reproducing video signals, audio signals and others.
2. Description of the Background Art
One known digital VTR is disclosed in Japanese Patent Application Laid-Open No. 3-217179 (1991), in which data associated with the recording contents stored on a tape are recorded in a start end part of the tape. Reference is made to FIG. 1 for explaining the record format of a magnetic tape and the arrangement of recording regions for various record signals throughout the magnetic tape, according to the above prior art. FIG. 1(a) shows the arrangement of recording signals stored within one track of the magnetic tape. One track is divided into several regions. Specifically, inward from the start end of the track are a video data region, audio data region, servo-pilot signal region and sub code region. The sub code region is further divided into several regions, that is, a region for data detection synchronization (SYNC), a region for-track numbers etc. (ID), a region for symbol and character data etc. (addition data) and a recording region (parity) for error-correcting codes. FIG. 1(b) shows the location of the recording regions for record signals in the entire tape. Specifically, (P1) through (Pn) denote recording regions for recording n-number of programs composed of video and audio signals, and (A1) through (An) denote recording regions for recording addition data for the above n-number of programs. The tape is also divided width-wise into a region (S1) for recording video and audio data and a region (S2) for recording addition data, and divided length-wise into a region (A) for recording addition data collected from respective programs and an ordinary recording region. During reproducing, information on the recording contents is obtained, by obtaining addition data from the region (A).
As a prior art in which data for the recording contents of a tape are stored in a start end of the tape, the following analog VTR adopting the VHS method is known. In this prior art, by the use of an A/D converter, reproducing video signals for one screen are converted into digital data and stored in a memory, and when a plurality of screens are stored, those screens are all reduced in size so as to be stored and displayed in one screen (multi-screen). Then, such a multi-screen is recorded in the start end of the tape by insertion. In reproducing, the multi-screen thus recorded by insertion is reproduced in order to obtain information on the recording contents.
There is known still another prior art, of which idea can be easily imagined from the above two conventional examples. In a digital VTR according to this method, a part of the video and audio data of each program to be recorded on a tape is stored in the start end of the tape using the same format as that of the program.
Japanese Patent Application Laid-Open 3-217179 (1991) teaches a method as described above, and it has therefore disadvantages in that: only addition data are reproduced from the start end of the tape, but video data and audio data stored in the large part of the tape cannot be confirmed at all. In order to confirm the video and audio data, it is necessary to execute reproducing, after moving the tape based on the addition data until the position where the above data are recorded is reached. This is troublesome and requires much time. The prior art adopting the VHS method is also disadvantageous, because although video signals can be confirmed at the start end of the tape, it is hard to see screens since the size of a screen is reduced as the number of screens is increased. Another disadvantage of this method is that sound cannot be confirmed.
The method, in which a digital VTR records a part of data for each program in the start end of a tape with the same format as that of the record format used for each program, has the following problem. Generally, the contents of a video signal can be identified by reading one frame or one field, whilst the contents of an audio signal cannot be identified within the time (i.e., 1/30 second or 1/60 second), within which a video signal can be identified. In order to identify the contents of an audio signal, a couple of seconds or more are needed. It is desirable to take a time as short as possible to identify the data stored in the start end of the tape. If the recording time is set on condition that video signals can be identified, audio signals cannot be identified at all. On the other hand, if the recording time is set on condition that audio signals can be identified, much time will be wasted when identifying the contents of most video signals.
Referring to FIG. 2, a prior magnetic recording and reproducing apparatus will be hereinafter described.
In recent years, the number and contents of programs recorded by a magnetic recording and reproducing apparatus need to be written down on labels or the like, or memorized by the user. The following is a description of a method in which a program is retrieved by the use of a prior magnetic recording and reproducing apparatus. First, the operation at the time of recording will be explained. In recording, an index signal is recorded in the beginning of a program to be recorded, especially in a particular position which is intended to be retrieved when reproducing. Such an index signal is automatically recorded at the start of recording, or arbitrarily recorded at any time. In this case, the recording of an index signal is performed in such a way that the user inputs index signal recording data through an operation unit 51. The operation data from the operation unit 51 are entered in a control unit 52 and then the control unit 52 controls a CTL signal processor 53. The CTL signal processor 53 records an index signal for several seconds, the index signal being obtained by changing the duty ratio of a CTL signal (a control signal for the beginning of each program). Accordingly, one tape can be divided for storing a plurality of programs by the use of index signals.
Next, the retrieval operation will be explained. The user retrieves a program by operating index retrieval keys on the operation unit 51, the index retrieval keys consisting of a key for retrieving in the forward direction and one for retrieving in the backward direction. When depressing the forward index retrieval key for example, input data are sent through the operation unit 51 to the control unit 52 and the control unit 52 controls a running control unit 55 through a motor drive servo circuit 54, whereby the tape is rapidly traversed. The CTL signal reproduced at that time is supplied to an index discriminating circuit 56, and upon finding of an index signal, an index discovery signal is sent to the control unit 52. Upon receipt of the index discovery signal, the control unit 52 controls the motor drive servo circuit 54 and a reproducing circuit 58 as follows. After the motor drive servo circuit 54 has allowed the running control unit 55 to stop the rapid traverse and to rewind the tape up to the position where an index signal is stored, the apparatus is set in "reproducing" mode. When the apparatus is in "reproducing" mode, the reproducing circuit 58 amplifies the signal reproduced from a head and changes it back to the original video signal to release as an output. An image is produced on a TV receiver 64 based on the video signal, thereby completing the data retrieval. If the user depresses two times the index retrieval key on the operation unit 51 for example, the retrieval operation will be performed until two index signals are found. The index search in the backward direction can be performed in a similar fashion. In this case, the retrieval is performed in the direction that the tape is rewound.
Besides the above-described method, the following retrieval methods are known. In one known method, the duty ratio of a CTL signal is precisely controlled and set to be address data, and the location of each program is represented by an absolute address. In data retrieval, the program can be directly retrieved by inputting the address data by the user. Another method is such that a CTL signal is precisely controlled and set to be linear time counter data, and a recording time is recorded on the tape. In data retrieval, the user inputs a counter value of the beginning of a program, whereby the program can be directly retrieved.
Because the conventional magnetic recording and reproducing apparatus are designed as described above, they have the following disadvantages: in order to retrieve a desired program the user has to employ a troublesome procedure in that the contents of a magnetic tape must be previously memorized or written down on labels, and then the desired program is retrieved with the help of the user's memory or by referring to the labels.
In the case of the arrangement in which a program can be directly selected, an encoder and a decoder are required for dealing with address data for precisely controlling the duty ratio of a CTL signal or linear time counter data. This increases not only the scale of the circuit but also the production cost.
In recent years, apparatus for recording and reproducing video signals such as video tape recorders have been extensively used in broadcasting stations as well as for amateur use in the home. Most families use a number of cassette tapes which are a recording medium for such apparatus. Therefore, there has been a growing demand for a method and apparatus in which the recording contents of a cassette tape be easily confirmed and data retrieval can readily performed. A magnetic recording and reproducing apparatus, in which a multi-screen is prepared from video signals for the purpose of performing confirmation of the recording contents and data retrieval, is disclosed in Japanese Application Laid-Open 63-4478 (1988). The structure and operation of this apparatus will be described below.
FIG. 3 shows a block diagram of the aforesaid magnetic recording and reproducing apparatus. Firstly, in recording, an address is set by an operation unit 71 at a tape position which is intended to be detected at the start of recording or especially in reproducing, and a driving switch is turned. The switch data and address data entered through the operation unit 71 are supplied to a control unit 72, and then, the control unit 72 releases an output of conversion data to a control record signal processor 74 according to the address data The control record signal processor 74 records a control record signal on a magnetic tape in compliance with the conversion data from the control unit 72.
Thereafter, a high-speed search button on the operation unit 71 is depressed. The output of the button data from the operation unit 71 is entered in the control unit 72 and the control unit 72 sends a command to a motor drive servo circuit 76 in order to bring a running control unit 77 into its high-speed running state. The running control unit 77 starts high-speed running, being in a sub-loading condition. In the course of the high-speed running, a control signal duty discriminating circuit 73 amplifies a reproduced control signal, shapes its waveform and discriminates the duty ratio.
If address data recorded on the magnetic tape are found, they are supplied to the control unit 72. After having been supplied with the address data, the control unit 72 sends a command to the motor drive servo circuit 76 and to a reproducing circuit 75 in order to bring the running control unit 77 into its reproducing state. After the running control unit 77 has been brought into the reproducing state, the motor drive servo circuit 76 controls a motor such as a capstan motor or a cylinder motor in accordance with a reproducing control signal. In the reproducing circuit 75, a reproduced signal from the head is amplified and changed back to the original video signal. The video signal thus obtained is released to a memory circuit 79. After image data have been released, the control unit 72 sends a command to a memory control circuit 80 so that the memory control circuit 80 controls the memory circuit 79 to store the image data and the address data. In compliance with the command from the control unit 72, the memory control circuit 80 controls the memory circuit 79 so as to thin the video data and the address data and to store them at a part thereof. After the data have been reproduced for a certain period of time, the running control unit 77 is set in the high-speed running state again.
The above operation is repeated several times, thereby storing in the memory circuit 79 image data recorded in several positions whose address data are stored. The control unit 72 detects whether one field or one frame of the memory circuit 79 is fully filled with data, or whether the magnetic tape is completed. After the detection, the control unit 72 sends a command to the motor drive servo circuit 76 so as to go back to the start end of the tape. After the start end of the magnetic tape has been regained, the running control unit 77 is set in the recording state.
The contents of data in the memory circuit 79 are recorded on the magnetic tape, by connecting the memory circuit 79 to the recording circuit 82 by means of a record signal change-over switch 84 and by connecting the recording circuit 82 to the head by means of a recording/reproducing change-over switch 83. When retrieving the tape position, the start end of the magnetic tape is stored in the memory at the same time that an image is formed on a TV receiver 78 based on the reproducing video signal, and after the address of the next tape position to be retrieved has been set based on the image data and address data, high-speed running is executed. The control unit 72 allows the running control unit 77 to be in the reproducing state when the set address becomes coincident with the address data recorded on the magnetic tape. After the running control unit 77 has been set in the reproducing state, a reproducing signal change-over switch 81 is turned so that an image based on the video signal from the reproducing circuit 75 is formed on the TV receiver 78. When performing tape position retrieval again, the reproducing signal change-over switch 81 is turned, an image based on the video signal from the memory circuit 79 is formed on the TV receiver 78, an address setting for the tape position retrieval is executed, and high-speed running is executed. The tape position retrieval is thus performed with the above-described procedure.
According to the above prior magnetic recording and reproducing apparatus, index signals are manually additionally recorded on a magnetic tape in which programs have been already recorded, and video signals from positions where index signals have been recorded are reproduced for preparing a multi-screen. Therefore, in order to prepare a multi-screen, the user has to preliminarily record individual index signals, while consulting reproduced image signals for confirmation. This makes the operation very troublesome and time-consuming. According to the other known method, indexes are automatically recorded at the start of recording and data in the positions where the indexes have been recorded are successively reproduced for preparing a multi-screen. In such a method, when timer recording is performed, the positions where an index is to be recorded mostly include commercials, because commercials are generally put on the air before and after a program. As a result, the most of the screens in the multi-screen depict commercials which are not suitable for program retrieval.
There is a method for performing retrieval with the recording contents on a cassette tape being displayed, wherein images at indexed positions of a medium in which video signals have been recorded are stored in the memory and then the images thus stored in the memory are displayed on a monitor screen and used for retrieval. One example is disclosed in Japanese Patent Application Laid-Open No. 63-102092 (1988). The method disclosed in the above publication will be explained below.
FIG. 4 is a block diagram of the aforesaid prior magnetic recording and reproducing apparatus. In recording, a program search signal driving switch provided on an operation unit 101 is turned at a position which is intended to be detected at the start of recording or particularly in reproducing. The switch data entered through the operation unit 101 are supplied to a control unit 102 and the control unit 102 sends a program search signal write-in command to a control record signal processor 104. In accordance with the command, the control record signal processor 104 records, on a magnetic tape, a control record signal whose duty ratio has been changed.
During reproduction, a high-speed search button on the operation unit 101 is depressed and a counter 112 is reset at that time. After being provided with the switch data from the operation unit 101, the control unit 102 sends a command to a motor drive servo circuit 106 in order to set the running control unit 107 in its high-speed running state. The running control unit 107 starts high-speed running while being in a sub-loading condition. In the course of the high-speed running, a control signal duty discriminating circuit 103 amplifies a reproduced control signal shapes its waveform and discriminates the duty ratio. When a program search signal is detected, the control signal duty discriminating circuit 103 releases a signal to the control unit 102 indicating whether a program search signal is present or absent.
The control unit 102 receives the data as to the presence/absence of a program search signal If a program search signal is present, the control unit 102 stores a tape count value at that time from the counter 112 and sends a command to the motor drive servo circuit 106 and a reproducing circuit 105 in order to bring the running control unit 107 into its reproducing state. After the running control unit 107 has been set in the reproducing state, a reproducing signal change-over switch 111 is connected to the side of the reproducing circuit 105 and the motor drive servo circuit 106 controls, in accordance with a reproduced control signal, a motor such as a capstan motor or cylinder motor. The reproducing circuit 105 amplifies the reproduced signal from the head and changes it back to the original video signal in order to supply it to a memory circuit 109. After video data has been released, the control unit 102 sends a command to a memory control circuit 110 so as to supply the video data and address data to the memory circuit 109. The memory control circuit 110 controls the memory circuit 109 in compliance with the command from the control unit 102 such that the memory circuit 109 stores, in a part thereof, a reduced image of a large screen to be reproduced at the time of reproducing.
FIG. 5 is a diagram showing a display pattern of a TV receiver. The reduced image is stored in a part of the memory circuit 109, that is, the left top part indicated by ADR.1. After the writing of the data in the memory circuit 109 has been completed, the running control unit 107 is set in its high-running state again, and the reproducing signal change-over switch 111 is connected to the side of the memory circuit 109.
The above operation is repeatedly performed several times so that the reduced images of large screens to be reproduced at the time of reproducing are successively stored in a part of the memory circuit 109, the part being divided into an N-number of regions. Each time a reduced image is stored, a tape count value from the counter 112 is stored in the control unit 102. The control unit 102 detects whether the memory circuit 109 is fully filled with data or whether the magnetic tape is completed. After the detection, the control unit 102 sends a command to the motor drive servo circuit 106 so as to stop the running of the magnetic tape. At that time, the reproducing signal change-over switch 111 is connected to the side of the memory circuit 109 and images based on picture signals from the memory circuit 109 are formed on a TV receiver 108 as shown in FIG. 5.
In retrieving a tape position, the user specifies a tape position by depressing a corresponding ADR number switch on the operation unit 101, viewing images which have been formed on the TV receiver 108 based on the data from the memory circuit 109. Based on the switch data from the operation unit 101 and the tape count value stored in the control unit 102, the tape position is retrieved. When the apparatus is in "reproducing" mode, the switch 111 is turned so that an image based on a signal from the reproducing circuit is formed on the TV receiver 108. If tape position retrieval is again performed, the switch 111 is turned so that images based on the signals from the memory circuit 109 as shown in FIG. 5 are formed on the TV receiver 108. Then, an ADR number on the screen is read and this number is specified through the operation unit 101 for the next retrieval.
Because the prior magnetic recording and reproducing apparatus is designed as described above, the actual retrieval operation is inconvenient and time-consuming, that is, reading of an address number composed of one to five digits from the screen, and input operation of entering this number through the operation means. When the number of small screens on the multi-screen is increased, the operation becomes even more inconvenient. For example, when the number of small screens is 16, an address number composed of at least two digits needs to be read from the screen and input by means of the operation unit 101. Furthermore, since a screen becomes small in size, with an address number composed of an increased number of digits, a large part of the image is obscured because the image is behind the address number. Another known method is that operation buttons corresponding to respective small screens on the multi-screen are employed for specifying a desired image on the multi-screen. However, this method also has the following disadvantages: (i) the provision of such buttons increases the production cost; and (ii) in a case where there are a large number of small screens, the number of buttons increases as a matter of course, and therefore it becomes difficult for a user to operate the buttons corresponding to the screens.